linux-kernel - Re: [PATCH 1/3] x86/resctrl: Get max rmid and occupancy scale directly from CPUID instead of cpuinfo

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Date:   Mon, 17 Jun 2019 09:52:14 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, H Peter Anvin <hpa@...or.com>,
        Christopherson Sean J <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        x86 <x86@...nel.org>, Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH 1/3] x86/resctrl: Get max rmid and occupancy scale
 directly from CPUID instead of cpuinfo_x86

On Sun, Jun 16, 2019 at 08:18:09PM -0700, Fenghua Yu wrote:
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index 2c57fffebf9b..f080be35da41 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -801,6 +801,31 @@ static void init_speculation_control(struct cpuinfo_x86 *c)
>  	}
>  }
>  
> +static void get_cqm_info(struct cpuinfo_x86 *c)
> +{
> +	if (cpu_has(c, X86_FEATURE_CQM_LLC)) {
> +		u32 eax, ebx, ecx, edx;
> +
> +		/* QoS sub-leaf, EAX=0Fh, ECX=0 */
> +		cpuid_count(0x0000000F, 0, &eax, &ebx, &ecx, &edx);
> +		/* will be overridden if occupancy monitoring exists */
> +		c->x86_cache_max_rmid = ebx;
> +
> +		if (cpu_has(c, X86_FEATURE_CQM_OCCUP_LLC) ||
> +		    cpu_has(c, X86_FEATURE_CQM_MBM_TOTAL) ||
> +		    cpu_has(c, X86_FEATURE_CQM_MBM_LOCAL)) {
> +			/* QoS sub-leaf, EAX=0Fh, ECX=1 */
> +			cpuid_count(0x0000000F, 1, &eax, &ebx, &ecx, &edx);
> +
> +			c->x86_cache_max_rmid = ecx;
> +			c->x86_cache_occ_scale = ebx;
> +		}
> +	} else {
> +		c->x86_cache_max_rmid = -1;
> +		c->x86_cache_occ_scale = -1;
> +	}
> +}
> +
>  void get_cpu_cap(struct cpuinfo_x86 *c)
>  {
>  	u32 eax, ebx, ecx, edx;
> @@ -832,33 +857,6 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
>  		c->x86_capability[CPUID_D_1_EAX] = eax;
>  	}
>  
> -	/* Additional Intel-defined flags: level 0x0000000F */
> -	if (c->cpuid_level >= 0x0000000F) {
> -
> -		/* QoS sub-leaf, EAX=0Fh, ECX=0 */
> -		cpuid_count(0x0000000F, 0, &eax, &ebx, &ecx, &edx);
> -		c->x86_capability[CPUID_F_0_EDX] = edx;
> -
> -		if (cpu_has(c, X86_FEATURE_CQM_LLC)) {
> -			/* will be overridden if occupancy monitoring exists */
> -			c->x86_cache_max_rmid = ebx;
> -
> -			/* QoS sub-leaf, EAX=0Fh, ECX=1 */
> -			cpuid_count(0x0000000F, 1, &eax, &ebx, &ecx, &edx);
> -			c->x86_capability[CPUID_F_1_EDX] = edx;
> -
> -			if ((cpu_has(c, X86_FEATURE_CQM_OCCUP_LLC)) ||
> -			      ((cpu_has(c, X86_FEATURE_CQM_MBM_TOTAL)) ||
> -			       (cpu_has(c, X86_FEATURE_CQM_MBM_LOCAL)))) {
> -				c->x86_cache_max_rmid = ecx;
> -				c->x86_cache_occ_scale = ebx;
> -			}
> -		} else {
> -			c->x86_cache_max_rmid = -1;
> -			c->x86_cache_occ_scale = -1;
> -		}
> -	}

Why are you doing this carving out into a separate function since you're
keeping the cpuinfo_x86 members?

-- 
Regards/Gruss,
    Boris.

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